| 摘要 |
A rod coupling formed of a tubular housing having a first box end and a seco nd box end. The tubular housing has an interior surface defining a bore extendi ng along the tubular housing from the first box end to the second box end, and has an exterior surface. Plural openings extending transversely through the housing from the interior surface to the exterior surface. A coating on the exterior surface of the tubular housing covers the plural openings, and may fill the openings or extend through the openings to form knobs inside the tubular housing. The coatings may taper from the exterior surface towards the interior surface. The openings are preferably distributed uniformly around the tubular housing. The openings are preferably distributed in plural rows. A rod string may be made up of plural such rod couplings and connecting rods.
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